Temperature control apparatus



Nov. 14, 1950 Filed April 22, 1947 J- A. M LEAN, JR

TEMPERATURE CONTROL APPARATUS 2 Sheets-Sheet 1 WITNESSES:

lNVENTOR JOHN A. MLEAN JR.

ATTORNEY 1950 J. A. MOLEAN, JR 30,338

TEMPERATURE CONTROL APPARATUS Filed April 22, 1947 2 Sheets-Sheet 9 WITNESSES:

INVENTOR JOHN G. MCLEAN IR.

g QM ATTORN EY Patented Nov- 14, 1950 2,530,338

UNITED STATES PATENT OFFICE TEMPERATURE CONTROL APPARATUS John A.McLean, J r., Springfield, Mass., assignor to Westinghouse ElectricCorporation, East Pittsburgh, Pa., a corporation of PennsylvaniaApplication April 22, 1947, Serial No. 743,049

2 21 formed of two metal sheets 28 and 30 which are welded together.embossed to provide refrigerant passages 32, a refrigerant inlet 34 tosaid passages 32, and re- It is an object of the invention to provide a5 frigerant headers 36. The cooling unit 26 also control system for theprimary refrigerating comprises a metal top plate 38 and a metal rearapparatus in a refrigerator employing a secondplate 48 secured to thetop edges and the rear ary volatile refrigerant circuit, which systemedges, respectively, of the U-shaped element 21. maintains satisfactorytemperatures for freezing A convoluted metal refrigerant tube 42 isfoods. brazed to the upper surface of the top plate 38 It is anotherobject of the invention to provide and the rear surface of, the rearplate 48 and a control system for a refrigerator of the typecommunicates at its lower end with the inlet 34 described, which systemmaintains substantially of the U-shaped element 21. The cooling unituniform temperatures in spite of variations in here described is morefully shown and described ambient temperatures. in the patentapplication, Serial No. 668,950 of It is a further object of theinvention to pro- Jues N. Saler, filed May 10, 1946. vide a controlsystem for a refrigerator of the The cooling unit 26 is adapted forfreezing type described, in which the thermostat may foods and issupplied with a volatile refrigerant have a large temperaturedifferential. liquid by the refrigerant apparatus 28 in the These andother objects are effected by the lower compartment It. The apparatus 20cominvention as will be apparent from the following prises a sealedcasing 44 enclosing a compressor description and claims taken inconnection with and an electric motor for driving the compressor. theaccompanying drawings, forming a part of A suction tube 46 connects thecasing 44 with one this application, in which: of the headers 36. Thecompressor withdraws Fig. 1 is a view in elevation of a refrigeratorrefrigerant vapor from the header 36 through with parts broken away andembodying the the suction tube 46, compresses the vapor, and invention;forces it through a tube 48 into a condenser 56 Fig, 2 is a, sectionalview on th li 11-11 or wherein the refrigerant vapor is liquefied. TheFig, 1; and refrigerant liquid flows through a capillary tube Fig. 3 isa view in perspective of the secondary 30 52 to the tube 42 wherein aportion of the rerefrigerant circuit and a phantom view of the r tliquid Vaporizes- The remaining einner liner of the refrigerator cabinetto whic frlgerant liquid and the refrigerant p r Pa s the secondarycircuit is secured. to the inlet 34 of the U-shaped element 21 where-Referring now to the drawings for a description in the completevaporization o the efrigerant of the invention, the reference numeral I0desig- 35 liquid takes p nates the outer metal, shetl of a refrigeratorh low r p r n f t upp mpartment cabinet l2. A horizontal partition l4divides the IB is maintained at a t p rature of about 0 cabinet l2 intoan upper compartment [6 for the F. and constitutes the area where frozenfoods freezing and storing of frozen foods and a lower y be s d- Thisportion is cooled by a concompartment l8 for the refrigerantsupplying 40Ventional flow 0f from the cooling it 26 apparatus 20. The uppercompartment l6 comand also by a secondary volatile refrigerating priseson inner metal liner 22 spaced from the circuit 54. The secondarycircuit 54 consists of outer metal shell I!) and the partition l4. Ther-9. closed tube which has been evacuated and mal insulating material isdisposed between the fi l d partially with a volatile refrigerant liquidside, rear, and top walls of the inner liner 22 and through the fillerpipe 55. The secondary circuit the corresponding walls of the outershell I3. 54 includes a first portion 56 lying adjacent to Thermalinsulating material 24 is also disposed and in heat-transfer relationwith some of the betweenthe bottom wall of the inner liner 22 andconvolutions of the tube 42 on the rear plate 48 the partition l4. Adoor 25 of similar construcof the cooling unit 26. The first portion 56tion closes the front opening of the cabinet I2. 50 serves to condenserefrigerant vapor into a.

A primary evaporative cooling unit 26 is seliquid. The secondary circuit54 also comprises cured, by means not shown, in the upper portion asecond portion 58 secured to the side, rear and of the upper compartmentIS. The cooling unit bottom walls of the inner liner 22. The sec- 26 maybe of any convenient design but is here 0nd. portion 58 cools the uppercompartment shown as comprising a broad U-shaped element 55 I6 andabsorbs the heat which penetrates The sheets 28 and 30 are accuses 3through the thermal insulation 24 thereof. The secondary circuit alsoincludes a third portion 66 which conducts the vaporized refrigerantfrom the second portion 58 to the first portion 66 of the secondarycircuit 64. The secondary circuit 54 also comprises a fourth portion 62for conducting the refrigerant liquefied in the first portion 56 to thesecond portion 66. A part 64 of the fourth portion 62 lies in thethermal insulation 24 of the refrigerator cabinet l2 and out of thermalcontact with other portions of the refrigerator so that the temperatureof part 64 correspond substantially to the temperature of therefrigerant flowing therethrough. A tube 66 is intimately brazed to thepart -64 for a purpose which will be explained subsequently.

The electric motor in the sealed casing 44 of the refrigerant-supplyingapparatus 20 is energized through the electrical leads 66 and athermostatic control is interposed in one of the leads 68. The control10 comprises a switch 12 actuated by a metal bellows 14 through anover-center spring 16 which affords a snapacting movement to the switch12 in a manner well understood in the art. The metal bellows l4communicates through a tube 18 with a bulb 66 located in the tube 66.

The bellows 14, the tube I8, and the bulb 66 are evacuated and chargedwith a small quantity of a volatile liquid so that the pressure withinthe bellows I4 is responsive to the temperature of the liquid in thebulb 60 when the refrigerant apparatus 20 is in operation. It will thusbe apparent that the switch 12 is opened and closed in response to thetemperature of the bulb 80 and that the switch 12 controls the operationof the electric motor and hence of the compressor to actuate thecompressor whenever the temperature of the bulb so rises above apredetermined temperature such as 1 F. and stops the compressor wheneverthe temperature of the bulb 80 is reduced to a second predeterminedtemperature such as minus 7 F. Since the temperature of the bulb 60corresponds to the temperature of the part 64 of the secondary circuit,the refrigerating apparatus 26 is controlled by the temperature of therefrigerant flowing therethrough.

The advantages of placing the thermostatic bulb 80 in heat transferrelationship with the refrigerant liquid flowing through the part 64 areas follows:

First, when a large quantity of food is placed in the primaryevaporative cooling unit 26 to be frozen, the refrigerating apparatus 26will run substantially continuously. This is caused by the fact that therefrigerant liquid in the primary cooling unit 26 is vaporized rapidlyby the relatively warm food. This tends to raise the suction pressure ofthe refrigerant supplying apparatus 20 since its pumping capacity islimited. The increased suction pressure causes the temperature of therefrigerant in the tube 42 to rise, and the part 64 of the secondarycircuit is not cooled to the assumed temperature of minus 7 F. at whichthe thermostatic control I6 stops the compressor. The refrigeratingapparatus 26 is thus caused to operate at its maximum capacity to freezethe food.

Second, the thermostatic control 10 may be of the wide temperaturedifferential type, the temperature differential between starting andstopping the apparatus 20 being about 8 F. This is caused by the factthat the changes in the temperature of the part 64 are closely related 4to the changes in the temperature of the primary cooling unit 26vbecause the refrigerant liquid" condensed in the first portion 66 by theprimary cooling unit 26 flows directly through part 64. The changes intemperature of the primary cooling unit 26, in turn, are directlyresponsive to the running cycles of the refrigerant apparatus 20, sothat the temperature of part 64 normally drops when the refrigeratingapparatus 20' is in operation and rises when said apparatus stops.

Third, the location of the bulb on the secondary refrigerant circuitinsures a constant temperature in the frozen food storage area of theupper compartment l6 when the ambient temperature of the refrigeratorvaries. It will be readily apparentthat if the temperature of therefrigerant liquid supplied to the second portion 66 of the secondarycircuit 54 is held between the aforementioned predetermined limits, thetemperature of this portion 58 will also be held substantially to theselimits in spite of changes in the heat load caused by increases in theambient temperature. This alone would not keep the temperature in thestorage area substantially constant because the increased heat leakagethrough the walls of the cabinet not cooled by the portion 58 of thesecondary circuit 56 (such as the door 25, the upper wall, and the upperportions of the side and rear walls of the compartment l6) would allowadditional heat to leak in. This additional heat leakage, however, isoffset by the lower temperature at which the primary cooling unit 26 isforced to operate to absorb all of the heat supplied by the firstportion 56 of the secondary circuit 54. This lower temperature of theprimary cooling unit 2|] thus additionally cools the storage compartmentby convection and tends to hold its temperature constant.

Fourth, the temperature of the frozen food storage area tends to remainconstant if relatively warm foods are placed therein, since the primarycooling unit 26 will be forced to operate at a lower-temperature underthese conditions to absorb all the heat supplied by the secondarycircuit 54 as explained above.

It will be apparent from the above that this invention provides alocation for the control bulb of a refrigerator utilizing a secondaryrefrigerant circuit, which location affords rapid freezing of foods inthe primarycooling unit, a substantially constant temperature in thefood storage area, and allows the use of a wide differential control.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications without departing from the spiritthereof.

What I claim is:

1. In refrigerating mechanism, the combination of a primary evaporator,apparatus for supplying said primary evaporator with a volatile liquidrefrigerant and for withdrawing vaporized refrigerant from saidevaporator, thermostatic control for rendering said apparatus active andinactive, and a secondary volatile refrigerant circuit operating at thesame pressure throughout, said secondary circuit having a first portionin heat transfer relationship with said primary evaporator forcondensing refrigerant vapor in said secondary circuit, said circuithaving a second portion for absorbing heat to vaporize refrigerantliquid in said circuit, said secondary circuit having a. third portionfor conducting refrigerant vapor from said second portion to said firstportion, said circuit also having a fourth portion for conductingrefrigerant liquid from said first portion to said second portion, saidthermostatic control including a temperature-responsive actuatingelement in heat-transfer relationship substantially solely with saidfourth portion of said circuit.

2. In a refrigerator, the combination of a thermally insulated chamber,a primary evaporator for cooling said chamber, refrigerating apparatus.

far supplying said primary evaporator with refrigerant liquid and forwithdrawing refrigerant vapor from said evaporator, a secondary volatilerefrigerant circuit operating at a uniform pressure throughout, saidcircuit having a first portion in heat transfer relationship with saidprimary evaporator, a second portion for cooling said chamber, a thirdportion for conducting refrigerant vapor from said second portion tosaid first portion, and a fourth portion for conducting refrigerantliquid from said first portion to said second portion, said fourthportion having at least a part which does not lie in directheat-conducting relationship with said primary evaporator, or with saidfirst, second, or third portion of the secondary circuit, and athermostatic control for rendering said apparatus active and inactive,said thermostatic control including a temperature-responsive actuatingelement lying in heat-transfer relation with said part of the fourthportion of said circuit.

3. The refrigerator structure defined in the immediately preceding claimwherein the primary evaporator is located within said chamber.

4. In a refrigerator, the combination of a chamber having metal wallsand thermal insulating material on the outer surface of said walls, aprimary evaporator in the upper portion of said chamber, refrigeratingapparatus for supplying said primary evaporator with refrigerant liquidand for withdrawing refrigerant vapor from said evaporator, a secondaryvolatile refrigerant circuit operating at a uniform pressure throughout,said circuit having a first portion in heat-transfer relationship withsaid primary evaporator, a second portion in heat-transfer relationshipwith extensive portions of said metal walls,-a third portion forconducting refrigerant vapor from said second portion to said firstportion, and a fourth portion for conducting refrigerant liquid fromsaid first portion to said second portion, said fourth portion having atleast a part which does not lie in direct heat-conducting relationshipwith any of said metal walls, with said primary evaporator or with saidfirst, second, or third portion of the secondary circuit, and athemostatic control for rendering said apparatus active and inactive,said control including a temperature-responsive actuating element lyingin heattransfer relationship with said part of the fourth portion ofsaid-circuit.

5. The refrigerator structure defined in the immediately preceding claimwherein said second portion is not in heat-transfer relationship withall of the walls of said chamber and wherein the primary evaporatorassists in cooling the chamber.

6. The refrigerator structure defined in the immediately preceding claimwherein said part of the fourth portion of said circuit and saidtemperature-responsive element are embedded in said thermal insulatingmaterial.

JOHN A. McLEAN. JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PA'I'ENTS

